1. Field of the Invention
The present invention relates to RFID tags for assigning computer-readable identification codes to actual articles, and in particular, relates to an RFID tag from which information on an article can be continuously obtained at many points on a route on which the article is moved.
2. Description of the Related Art
Recently, the use of radio frequency identification (RFID) tags that are a type of IC tag has been started. RFID tags are a tool that has a function similar to, for example, a function of tags that are attached to articles, i.e., a function of assigning unique identification codes to individual articles. Specifically, identification codes that can be read by, for example, computers are assigned to articles and are recognized by computers through radio communication (not an optical recognition method). In comparison with a case where known management methods are used in which, for example, tags or bar codes are used, in a case where RFID tags with such a recognition function are used, the efficiency of management of articles can be improved significantly.
In a general method for obtaining information related to articles from RFID tags, readers that read data from RFID tags are placed at key places, and information related to articles is obtained at (or near) the places where the readers are placed. Furthermore, as the use of RFID tags has increased, a demand has occurred that information on articles be continuously (successively) obtained at not only places where readers are placed but also many points.
For example, an RFID tag as shown in FIG. 1 is introduced as that satisfies the aforementioned demand.
The RFID tag shown in FIG. 1 includes a short-range RFID tag unit 270a that can perform communication in a relatively narrow range and a long-range RFID tag unit 270b that can perform communication in a broad range in a single RFID tag. Although the long-range RFID tag unit 270b can perform communication in a broad range (i.e., even when the long-range RFID tag unit 270b is distant from a reader, the long-range RFID tag unit 270b can perform communication), only an approximate location can be determined with the long-range RFID tag unit 270b. On the other hand, although the communication range of the short-range RFID tag unit 270a is narrower than that of the long-range RFID tag unit 270b, a detailed location can be determined with the short-range RFID tag unit 270a. The RFID tag shown in FIG. 1 includes such two different functions (especially, the effective range) in a single package so that the functions complement each other to enable continuous acquisition of pertinent information (for example, in a case where the RFID tag shown in FIG. 1 is attached to a person, information of the location of the person to whom the RFID tag is attached).
See, for example, Document 1: Japanese Patent Application Laid-Open No. 2004-46904 that disclosed a single RFID tag which include two types of RFID tag section.
The technique disclosed in aforementioned Patent Document 1 is a technique in which a single RFID tag includes two types of RFID tag sections, and a long-range RFID tag section is necessary. Thus, a problem exists in that the cost of the RFID tag is high compared with that of an RFID tag (that can perform only a short-range communication) that is generally used.
In general, an RFID tag is often discarded, remaining attached to an article (or detached from an article when management is not necessary). Thus, a high-cost RFID tag is not reused and is discarded, and this is not preferable in view of the economical efficiency. Moreover, regarding the environment, the following problem exists. In view of the amount of CO2 generated when an RFID tag is fabricated, it is highly probable that the RFID tag in Patent Document 1 is large compared with a general one, thereby causing increase in the amount of CO2 emissions in fabrication and increase in the environmental load.